There is a typo in section [c.math.fpclass], that is, "Classification / comparison functions". In C++23 it states "See also ISO/IEC 9899:2018, 7.12.3, 7.12.4." referring to C18 sections "Classification macros" and "Comparison macros". Reference to 7.12.3 is correct, however, section 7.12.4 is "Trigonometric functions". I interpret it should refer to the section 7.12.14 instead.

The typo seems to appear in the current draft too, as well as in the published C++23, C++20 and C++17 versions. In C++14 the section was organized in a different way and the reference was correct (paragraph 10). Thus, the typo might have been introduced in that section reorganization from C++14 to C++17.

Besides, it seems the section numbers have also changed in C23. To the best of my knowledge, C++26 will be based on C23 (i.e., ISO/IEC 9899:2024). In this case, sections "Classification macros" and "Comparison macros" are 7.12.4 and 7.12.18, respectively. Therefore, in order to fix this typo, I would say it would be enough to replace \xrefc{7.12.3, 7.12.4} with \xrefc{7.12.4, 7.12.18} in the file source/numerics.tex.

Since any new version of the C Standard may modify these section numbers, this kind of references might need to be double-checked before every new C++ final publication.